Piston rings have been used for some time with separate spring members as part thereof to provide outward urging of the sealing face of the ring against the wall of the cylinder in which it operates. A variety of configurations have been employed and all have a common problem which is generally referred to as "unitizing". As the term implies the ring and the spring member become united and consequently the spring loses a substantial portion of its ability to bias the ring. Typical examples of the prior art can be found in U.S. Pat. Nos. 2,729,524; 3,456,954 and 3,698,054.
It is an object of the present invention to provide a piston ring assembly comprising a ring and an expander spring member which exhibits superior performance in use and which has a substantially lower tendency to unitize than prior art devices.